2018/3/11 Where are we going 园上声哀通大学 CFD Simulation Models 国上清大学 CED has hecome a Lifting-line theory major de Panel codeAlsoknown as boundaryelement methods,fast,2D/3D Full Potential code Rotational terms dropped atom Navier-Stokes Equations Euler codes Viscous terms dropped Various turbulence models.RANS MDA and MDO in Cannot be analytically 品e solved so far Large Eddy Used on simplified geometries mprovements Supercomputing Direct Numerical Siulation (DNS) Largely research topic CFD simulation is usually a tradeoff among model fidelity,numerical accuracy and setup/computing time.Book to read "Computational Fluid Dynamics"by Anderson Aerodynamic Design Methods 圆上清文大些 Inverse design methods 圆上洋廷大蜂 Inverse design In inverse design methods,many designers prescribe the airfoil :eenet -Different flow models can be used f and define the o 0BI-8cnn-4p了 A baseline airfoil is selected as the starting point-some expertise is necessary to choose a good starting point -Two categor uasi-ewton,etc An iteration process is required to achieve convergence ary Methods: set as objectives and corstraints oernan Wen ong CFD-based Shape Optimization 国上清大学 How aircraft geometry was modelled 园上洋文大学 Input parameters(length,width,etc) Overall procedure used in CFD-based CAD Geometry aerodynamic optimization Mesh Generation Updated parameters (length,width,ete) Flow Solvers rslty-Dr.V(enbin Song 102018/3/11 10 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Where are we going 55 • CFD has become a major design tool, shape optimization is becoming more affordable • CFD needs to be developed in collaboration between Universities and Industry into a system of tools of various fidelity • MDA and MDO in industry settings will be one the key enablers for further improvements • Supercomputing continues to be an enabling factor © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics CFD Simulation Models Navier-Stokes Equations Cannot be analytically solved so far Lifting-line theory Panel code Euler codes Various N- S models Direct Numerical Simulation (DNS) Large Eddy Simulation Viscous terms dropped Various turbulence models, RANS Used on simplified geometries Also known as boundary element methods, fast, 2D/3D Largely research topic CFD simulation is usually a trade off among model fidelity, numerical accuracy and setup/computing time. Book to read “Computational Fluid Dynamics” by Anderson Full Potential code Rotational terms dropped © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Aerodynamic Design Methods • Inverse design – Different flow models can be used • Incompressible inviscid flow • Transonic potential flow • Euler and Navier-Stokes Model – Features: • Matching prescribed pressure distribution given by experienced engineers • Depends on the pressure distribution • More efficient compared to optimization methods • Optimization design – Two categories of methods • Gradient based approach: quasi-newton, etc – Control theory approach (Jameson) – Gradient computed using finite difference • Evolutionary Methods: genetic algorithms, etc – Features • Aerodynamic performances set as objectives and constraints • Optimized by shape modification based on different shape representations 57 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics Inverse design methods • In inverse design methods, many designers prescribe the airfoil pressure distribution cp on the airfoil and define the objective function to be minimized as • A baseline airfoil is selected as the starting point – some expertise is necessary to choose a good starting point • An iteration process is required to achieve convergence OBJ  (cpdesigni i1 N   cpactuali ) 2 © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics CFD-based Shape Optimization CAD Geometry Parameterization Mesh Generation (Discretization) Flow Solvers Input parameters (length, width, etc) Objective function and Constraints (lift, drag) Updated parameters (length, width, etc) Overall procedure used in CFD-based aerodynamic optimization Optimizers © Shanghai Jiao Tong University – Dr. Wenbin Song School of Aeronautics and Astronautics How aircraft geometry was modelled Source: D.G. Clark and A. Gibson, Concord, Phoebus Publishing Company, 1976/77